Preparation and purification of dinitroresorcinol



United States Patent PREPARATION AND PURIFICATION OF DINITRORESORCINOL Claude U. Alexander, Kampsville, Ill., and Emil Czapek,

New Haven, Conn., assignors to Olin Mathieson Chemical Corporation, East Alton, 111., a corporation of Virginia No Drawing. Application September 21, 1955, Serial No. 535,756

4 Claims. (Cl. 260-622) This invention relates to explosives and particularly to dinitroresorcinol and an improved method for the manufacture thereof.

The explosive properties of dinitroresorcinol have long been recognized and it has found extensive use as a component for fuses, ammunition priming compositions and other explosive devices. This material is normally prepared by the oxidation and nitration of dinitrosoresorcinol which in turn is a nitrosation product of resorcinol. The end product of the oxidation of the dinitrosoresorcinol consists predominately of dinitroresorcinol together with an appreciable amount of trinitroresorcinol. Dinitroresorcinol may also be prepared by the direct nitration of resorcinol, but in this case also, the end product is a mixture of dinitroresorcinol and trinitroresorcinol. Thus, regardless of the method of preparing dinitroresorcinol, the industry has been faced with the problem of separating it from the trinitroresorcinol with which it is invariably associated.

The terms dinitroresorcinol and trinitroresorcinol as used herein designate the commercially available isomers of these compounds, namely 2,4-dinitroresorcinol and 2,4,6-trinitroresorcinol.

In accordance with conventional practices, the dinitroresorcinol is separated from its mixtures'with trinitroresorcinol by recrystallization from hot water. Such a recovery process leaves much to be desired, for the amount of dinitroresorcinol obtainedbased on the theoretical amount available is usually between about and percent. In addition to the low yield, this recovery process also provides dinitroresorcinol having a melting point between about 125-137 C. whereas the melting point of pure dinitroresorcinol is generally reported to be 147148 C. It has long been recognized that the recrystallization of dinitroresorcinol from hot water was unsatisfactory because of the low yield and relative impurity of the product, but all previous efforts to improve the yield and purity of the dinitroresorcinol have failed.

It is therefore an object of this invention to provide a process for the preparation of dinitroresorcinol overcoming the disadvantages of the prior art processes. It is also an object of this invention to provide a novel process for the preparation of dinitroresorcinol. Another object of this invention is to provide an improved process for the separation of dinitroresorcinol from mixtures thereof with trinitroresorcinol and related compounds. A further object of this invention is to provide a process for the preparation of dinitroresorcinol having a high degree of purity. Another object of this invention is to provide an improved process for the separation of dinitroresorcinol and trinitroresorcinol. Other objects will appear from the following description.

In accordance with this invention dinitroresorcinol of high purity can be conveniently obtained in high yields from mixtures of dinitroresorcinol and trinitroresorcinol by preparing an aqueous slurry of the mixture, adjusting its pH to a value of at least about 2.0 and less than about 3.5, and separating the dinitroresorcinol from the solution. This invention is predicated on the discovery that trinitroresorcinol is converted to a water soluble form when subjected to an aqueous medium having a pH in excess of about 2.0. Thus, in accordance with this invention, dinitroresorcinol is separated from trinitroresorcinol by reducing the acidity of the mixture to above about pH 2.0 but less than pH 3.5. Within this pH range the trinitroresorcinol is rendered soluble while the dinitroresorcinol is maintained in its solid state and these two compounds can then be separated by physical methods, such as decantating, centrifuging, and filtering. While a separation of dinitroresorcinol and trinitroresorcinol is efiected when the pH is adjusted between 2.0 and below 3.5, the separation is much more eflicient when the acidity of the slurry is between about pH 2.9 and 3.0.

The neutralizing agent used to reduce the acidity of the mixture can be any suitable water soluble inorganic alkaline compound. In most instances it has been found convenient to use the oxides, hydroxides, carbonates and bicarbonates of the alkali metals and ammonium but other alkalies such as, for example, ammonia and its compounds can also be used.

The invention will be more fully understood by reference to the following specific examples of preferred embodiments thereof. 7

In accordance with this preferred embodiment, about parts by weight of resorcinol was nitrosated by the well known method of treating an acidified solution of resorcinol with sodium nitrite so as to form dinitrosoresorcinol and the resultant dinitrosoresorcinol was oxidized with nitric acid at about 0 C. in the conventional manner :so as to form crude dinitroresorcinol. This crude material was filtered and the resultantfilter cake, consisting essentially of a mixture of dinitroresorcinol and trinitroresorcinol, was added to about 1000 parts by weight of water at room temperature and agitated so as to form a slurry, with an acidity of about pH 1.7. During the continued agitation of the slurry, increments of 0.05 molar sodium carbonate solution were added until the acidity of the slurry was adjusted to about pH 3.0, as indicated with a pH meter. When the acidity of the slurry was reduced to this point the trinitroresorcinol therein went into solution leaving only the dinitroresorcinol suspended in the liquid medium. The slurry was then filtered to remove the dinitroresorcinol which was washed with distilled water so as to remove any trace of contaminants and then dried.

The material thus obtained was substantially pure dinitroresorcinol having a melting point between 147l48 C. This process yielded parts by weight of dinitroresorcinol which is 60 percent of that theoretically available, based on the amount of resorcinol originally used.

In repeated runs duplicating the above preferred embodiment, yields varying between 55 and 77 percent were obtained and, in each instance, the high purity of the product was attested by its melting point of 147-148 C. which is the reported melting point for pure dinitroresorcinol.

In order to illustrate even more clearly the efiicacy of the present invention in resolving mixtures of dinitroresorcinol and trinitroresorcinol, the following is a description of an experiment in which known proportions of these compounds were mixed together and then separated in accordance with the process of the present inven tion. In this example, parts are by weight unless otherwise specified.

About 10 parts of dinitroresorcinol and about 12 parts of trinitroresorcinol were sluried in 300 parts of water at room temperature. Meanwhile, about 5 parts of sodium carbonate were dissolved in about 100 parts of water. This carbonate solution was then gradually added to the aqueous slurry of dinitroresorcinol and trinitroresorcinol,

the pH of the slurry being measured frequently during the addition. The pH of the slurry prior to the addition of any of the carbonate solution was approximately 1.80 and after the addition of about 81 parts of, the sodium carbonate solution, the pH was increased to a value of 2.9 at which the trinitroresoreinol was rendered soluble. The pH was maintained at this value and the agitation continued for about 15 minutes to insure complete solution of trinitroresorcinol. The solution was then filtered and the dinitroresorcinol was retained on the filter paper, washed, dried and weighed. The filtrate was acidified with hydrochloric acid causing precipitation of the trinitroresorcinol. This material was also recovered by filtration and then Washed and dried. The amounts of dinitroresorcinol and trinitroresorcinol recovered were substantially equal to the amounts subjected to the process, making allowances for normal experimental error. The complete separation of these two materials was evidenced by their melting points which are substantially identical to the reported melting points of the pure materials. The melting point of the dinitroresorcinol thus separated was 147-148 C. and the melting point of trinitroresorcinol obtained from the mixture of this example was l79180 C.

From the above description and examples of the invention, it will be evident that the present invention constitutes a marked improvement over prior art methods for the preparation of dinitroresorcinol. In accordance with previous practices, the yield of dinitroresorcinol based on the resorcinol originally used normally varied between about and percent of a relatively impure product having a melting point between about 125-137" 0.; whereas this invention provides a process in which. the yield is between about 55 and 77 percent of a practically pure material having a melting point of 147-148" C.

It is therefore clear that the invention accomplishes its objects of providing a novel and improved process for the preparation of high purity dinitroresorcinol.

Having described the invention, what is claimed is:

1. In the manufacture of 2,4-dinitroresorcinol, the process of forming an aqueous slurry of nitration prod- 4 ucts containing a mixture of 2,4-dinitroresorcinol and 2,4,6-trinitroresoreinol, adjusting the pH of the slurry to above about'2.0 and less than 3.5 by intermixing therewith a Water soluble inorganic alkaline compound selected from the group consisting of ammonia and the oxides, hydroxides, carbonates and bicarbonates of the alkali metals and ammonium, and separating the 2,4- dinitroresorcinol from the slurry.

2. In the manufacture of 2,4-dinitroresorcinol the process comprising forming an aqueous slurry of nitration products containing 2,4-dinitroresorcinol and 2,4,6-

tiinitroresorcinol, adjusting the acidity of the slurry to at least about pH 2.0 and less than pH 3.5 by the addi tion of an aqueous sodium carbonate solution so as to effect a solution of the 2,4,6-trinitroresorcinol while maintaining the 2,4-dinitroresorcinol in suspension and separating the 2,4-dinitroresorcinol from the suspending liquid. 1

3. A method for segregating 2,4-dinitroresorcinol from mixtures of 2,4-dinitroresorcinol and 2,4,6-trinitroresorcinol which comprises agitating a mixture thereof in an aqueous solution a water soluble inorganic compound selected from the group consisting of ammonia and the oxides, hydroxides, carbonates, and bicarbonates of the alkali metals and ammonium having a pH of at least about 2.0 and less than pH 3.5 until the 2,4,6- trinitroresorcinol is dissolved and thereafter separating the liquid from the residue of 2,4-dinitroresorcinol.

4. A method of separating 2,4-clinitrores0rcinol from mixtures thereof with 2,4,6-trinitroresorcinol comprising adjusting the acidity of an aqueous slurry containing 2,4-dinitroresorcinol and 2,4,6-trinitroresoreinol to a value between pH 2.9 and pH 3.0 by intermixing therewith a water soluble inorganic alkaline compound selected from the group eonsitsing of amminia and the oxides, hydroxides, carbonates and bicarbonates of the alkali metals and ammonium, and separating the 2,4-dinitroresorcinol from the slurry.

References Cited in the file of this patent UNITED STATES PATENTS 2,301,912 Jones et a1. Nov. 10, 1942 

1. IN THE MANUFACTURE OF 2,4-DINITRORESORCINOL, THE PROCESS OF FORMING AN AQUEOUS SLURRY OF NITRATION PRODUCTS CONTAINING A MIXTURE OF 2,4-DINITRORESORCINOL AND 2,4,6-TRINITRORESORCINOL, ADJUSTING THE PH OF THE SLURRY TO ABOVE ABOUT 2.0 AND LESS THE 3.5 BY INTERMIXING THEREWITH A WATER SOLUBLE INORGANIC ALKALINE COMPOUND SELECTED FROM THE GROUP CONSISTING OF AMMONIA AND THE OXIDES, HYDROXIDES, CARBONATES AND BICARBONATES OF THE ALKALI METALS AND AMMONIUM, AND SEPARATING THE 2,4DINITRORESORCINOL FROM THE SLURRY 